Torque wrenches are commonly used to precisely set the torque of a fastener such as a nut or bolt, where the tightness of the fastener may be important. Some torque wrenches allow a user to also measure the torque (rotational force) applied to the fastener so that it may be matched to a torque specification.
A variety of torque wrenches have been developed, including mechanical types which may employ a beam that deflects under the applied torque, and electronic types which employ a strain gauge attached to a torsion rod. Some conventional torque wrenches employ a handle having a fixed head that includes a socket or other fitting for engaging the fastener. These fixed-head torque wrenches may not be suitable for use where the fastener is close to obstructions that interfere with grasping or rotating the handle. In these applications, it may be necessary to employ a torque wrench in which the head is pivotally attached to the handle by a hinge. The hinge allows the handle to be swung to a position where it may be freely rotated, out of the path of the obstruction. A problem may arise with these torques wrenches, which are sometimes referred to as “flexible head” torque wrenches, due to the fact that when the handle is swung away from a position in which it is axially aligned with the head, a portion of the force applied to the handle results in a force component that is not orthogonal to the rotational axis of the fastener. This “off-axis” force component may cause inaccuracies in torque readings.
Accordingly, there is a need for a torque wrench having a flexible head that provides accurate torque measurements irrespective of the off-axis, pivotal position of the handle.